1. Field of the Invention
This invention relates to a multilayered substrate and a method for its production. More particularly, the invention relates to a multilayered substrate having a core layer of a strong, hard-to-break material, but divisible into a plurality of parts, and a method useful for its production.
2. Description of the Prior Art
FIG. 5A is a plan view showing an example of a conventional multilayered substrate, and FIG. 5B is an enlarged sectional view taken along line V--V of FIG. 5A.
As shown in FIGS. 5A and 5B, a multilayered substrate 1 comprises a surface layer 2 laminated on each surface of a core layer 3 by the use of an adhesive (prepreg agent) 4. Between the core layer 3 and the surface layer 2, there is a printed wiring inner layer pattern (not shown) On the surface layer 2, there are a printed wiring superficial layer pattern (not shown), and various packaged electronic parts (not shown).
For the core layer 3, a plate comprising a glass fiber-woven cloth, as a core, hardened with an epoxy resin or the like is used to impart required strength to the multilayered substrate 1. The surface layer 2 which does not require marked strength, on the other hand, uses a thin plate comprising a cloth of glass fibers (a woven cloth), as a core, hardened with an epoxy resin or the like.
To divide the multilayered substrate 1 into a plurality of parts at predetermined positions of division, a plurality of V-grooves (grooves each with a V-shaped cross section) 5 formed by longitudinal and transverse linear V-cutting are present at the positions of division. In the illustrated example, the multilayered substrate 1 is severed along the V-grooves 5 to form body substrate portions A with packaged electronic parts, extra substrate portions B which have mounter basic holes 6 serving as references for packaging of electronic parts, and recognition marks 7 for setting a reference position for positioning during pattern formation. The body substrate portion A is further divided into a first body substrate portion A1 and a second body substrate portion A2.
FIG. 6A is a plan view showing another example of a conventional multilayered substrate, and FIG. 6B is an enlarged sectional view taken along line VI--VI of FIG. 6A.
As shown in FIGS. 6A and 6B, a multilayered substrate 11 comprises a surface layer 12 laminated on each surface of a core layer 13 by the use of an adhesive (prepreg agent) 14. Between the core layer 13 and the surface layer 12, there is a printed wiring inner layer pattern (not shown). On the surface layer 12, there are a printed wiring superficial layer pattern (not shown), and various packaged electronic parts (not shown).
For the core layer 13, a plate comprising a glass fiber-woven cloth, as a core, hardened with an epoxy resin or the like is used to impart required strength to the multilayered substrate 11. The surface layer 2 which does not require marked strength, on the other hand, uses a thin plate comprising a cloth of glass fibers (a woven cloth), as a core, hardened with an epoxy resin or the like.
To divide the multilayered substrate 11 into a plurality of parts at predetermined positions of division, slits 15 formed at spaced locations, and perforation-like holes 16 formed intermittently between the slits 15 and passing through the multilayered substrate 11 are present at the positions of division. In the illustrated example, the multilayered substrate 11 is severed along the slits 15 and the perforation-like holes 16 to form a body substrate portion C with packaged electronic parts, and an extra substrate portion D which has mounter basic holes 18 serving as references for packaging of electronic parts, and recognition marks 17 for setting a reference position for positioning during pattern formation. In the portion where the slits 15 are formed, perforation-like holes 16 may be formed instead of the slits 15.
With the above-described conventional multilayered substrates 1, 11, however, the core layers 3, 13 are made of a strong, hard-to-break material comprising a glass fiber-woven cloth as a core. Thus, the core layers 3, 13 do not easily break even when an operator tries to sever them by means of a simplified mold, or to divide them manually. Consequently, a dividing operation has been difficult. The surface layers 2, 12 are also made of a material comprising a glass fiber-woven cloth as a core, but can be easily divided, because they are thin.